Grounding mechanism for magnetos



Dec. 25, 1945. HARTZELL 2,391,854

GROUNDING MECHANISM FOR MAGNETOS Filed June 6, 1944 INVENTOR HIS ATTORNEYS Patented Dec. 25, E345 GROUNDING MEGHANISM FOR MAGNETOS- Hermani L. Hartzell,; Anderson, Ind., assignor-to.-

General -Motors- Corporation, Detroit,,,Mich., a,

corporation of Delaware Application June'G; 1944,'Ser-ia'l-No. 538,936

8 Claims: (Cl. 171,-209),

The present invention relates to connector units for the primary circuit of'magnetos' and more particularly to units for magnetos withpermanently connected generator windings so as to ture assembly are mounted in a metal housing to provide a unitary structure and wherein the conducting core of the condenser cooperates with the housing to form a ground connection when the terminal assembly is removed from the structure.

Another object of. the present invention. is to provide a. unitary structure, a combined condenser, unit and. terminal structure for electrical conductors, bywhich an improved. construction and arrangement of. parts is had, the structure having a. plurality of screw threaded connections, wherein in one device there is a pluralityof ground connections provided, together with means for suppressing interference withyoperation of adjacent radio apparatus,

Another object of the present invention is to providea, grounding device which is simple. compact, durable, and which may be readily-attached.

or removed and still be efiective in operationin all positions when mounted on the magneto.

Further objects and advantages of the present invention will be apparent from the following description reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown...

In the drawing:

Fig. l'is an endrview of the unitary grounding device embodying the present invention.

Fig. 2' is a sectional view taken on the line 22 of Fig. 1 and showing the device in its normal position.

Fig. 3 shows partly in section and partly diagrammatically, aplan View of a circuit interrupter mechanism having a housing which supports the grounding device.

Referring to the drawing, particularly Figs. 1 and 2, the grounding device In comprises a metal bushing or housing having a through bore 2|, constricted to provide shoulders of three difierent diameters; the largest portion of the borebeing at the-left endof the bushing, as viewed in Fig. 2; while the smallest portion ofthe-bore-is located intermediate the ends of the :bore-to-provide an internal ledge 23 to provide aground portion.

The larger portion-of the -bore-receivesa condenser assembly' 24 which includes a condenser body comprising two foil strips insulated-from each other by'a paper strip or strips 'wound upon anon-conducting-tube 25: a wellknown-construction' andarrangement. The right margin of one of the foils engages a-metal disc 26 while the left marginof the other foil engages a'metal cupmember. An, insulating disjc 28'and the condenser body is then assembledupon a conducting core 29 .with'. the disc 28ybearing againsta. shoulder siiprovided, by an enlarged portior1;,3l of the core. The enlargedportion 3! of the core carries a contact spring 32.. An apertured soft rubber washer 33, an apertured insulating disc 3'4and a metal washer 35arethen assembled. upon one end of the. core after which, said. end is riveted over as at 36 "against the washer 35 toclamp theelements 35; 34. 33, 2'1, 25, 29 between en- Iargedportion Bland the riveted-over portion. 36 of the core to complete the condenser assembly'.

Beforethe condenser'assembly is placed into one end of the bore 2| .an insulatinglining or sleeve 40, a;conducti-ng disc, 4| and, a conducting. resilient member or helical spring 43 are placed in a reduced portion of the bore H and arranged so that one end of sleeve 40 and the disc 4| will contact the-ledge or'shoulder 23. Itwilli be noted that the disc .4! and the spring 43-are smaller in cross dimension than theinternal diameter of the sleeve wthusthe disc 41 and the spring 43 can move axially relative to the sleeve 40, but the sleeve 40 prevents the washer and spring from moving laterally to contact the marginal side walls of thebushing 20. With "the sleeve ;40; disc 4| and spring 43 in position the condenser-assembly-2 5-is then positionedin this instance in the largest diameter-of-the bore with the washer adjacent ashoulder. The condenser assembly is then secured withinthe housing -byspinning over-a part-of the housing as at-44-againstthe insulation Washer 28: By this arrangement the spring provides theconducting connection be tween-- the core 29 and the disc 4|.

Theother end of the bore receives aterminal assembly comprising an insulating tube 5| having a portion of a hollow metal insert 52 embedded therein. The portion of the insert whichis-exposed is provided with threadsv on which is screwed a contact iii-which engages the" metal disc 4|. Before the contact 53 is attached to the insert a shielded cable 55 extends into the sleeve and insert and has bared end comprising strands spread outwardly over the end of the insert so that the strands are clamped between the end of the insert and the bottom of the tapped recess provided by the'contact 53. A rubber grommet 55 and an insulating washer 55 are threaded on the cable, said grommet engages the right hand end of the sleeve 5| while the washer 55 bears against the rubber grommet. The terminal assembly is secured within the bore of the housing by a nut 51 having internal threads engaging disc away from the ground shoulder 23 and thus 7 out of electrical contact with the housing 25 as shown in Fig. 2. The nut 51 is releasably locked in position by a spring finger 51a cooperating with serrations 5719 on the nut. Thus, when the grounding unit is assembled as shown in Fig. 3 electrical connection is maintained between a grounding switch 58 and a leaf spring 59 of a magneto 50.

Referring to Fig. 3 the magneto 65 has permanently connected primary and secondary generating windings 6| and 62, respectively, and a housing 63 for the circuit interrupter mechanism arranged in a circuit of the primary winding 6!. The circuit interrupter mechanism shown comprises a lever 65 having a rubbing block which is urged by a spring 65 into engagement with a lobe of a cam 5'! attached to a shaft 58 of a rotor of the magneto. The lever 55 is periodically operated by the lobes on the cam. Upon each operation of the lever the rubbing block engages a spring pressed arm 69 to separate carrying con tact from contact H attached to an ear 12 of a plate 13 adjustably mounted upon a plate 14. The plate"! is grounded to the housing 63 and the lever 69 is supported from a terminal i5 insulated from the plate M, said terminal is normally the live terminal of the circuit interrupter. The core 29 of the condenser assembly is connected with the terminal 15 by the leaf conductor 59 and thespring 32 to shunt the contacts l5 and H. The live terminal 75 is connected by wire TI to one end of the primary winding BI and one end of the secondary winding 62, The other end of the primary is grounded by the housing 63 and the other end of the secondary is connected to a distributor rotor 19 to distribute ignition voltage, generated by the magneto upon separation of contacts 10, H to the spark plugs 80 in the well known manner.

It is pointed out that when the grounding device I0 is removed from housing 63 the strap 59 which is biased will engage the housing 63 as indicated by the broken lines 59a. In the dot-and-dash position of the strap the magneto is grounded and renders same incapable of generating ignition voltage upon periodic separation of the contacts 10, H. When the bushing 20 is attached to the housing without the terminal assembly therein the magneto will be grounded even though the spring strap is not in contact with the housing because the strip will be electrically connected with the housing 63 through spring 32, condenser core 29, spring 43 and disc M which is forced against the metallic shoulder 23. When the terminal assembly is positioned within the bushing the contact 53 will engage the disc 4! to urge same from the shoulder 23, thus the magneto is rendered operative provided the cable is not grounded.

The cable 54 is electrically connected to the manually operated grounding switch 58, which may be operated at will to ground the magneto to deprive the engine of ignition.

Thus, as will be apparent to those skilled in the art, the magneto may be rendered incapable of generating ignition voltage in various ways; first, by removing the grounding device to allow the strap to engage the housing by its own resiliency;

bushing 20 sufiiciently to allow the disc A! to engage the shoulder 23 and third, by closing the switch 53.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow. p

What is claimed is as follows:

1. A condenser and magneto primary grounding unit adapted to be detachably attached to a magneto housing comprising, a metal body provided with a through opening and being internally restricted intermediate its ends to provide an abutment; a condenser unit having a metal core fixed in one endof the opening so that the inner end of the core is spaced from the abutment; a coil spring of conducting material disposed between the core and the abutment, said core, spring and abutment when in their normal position cooperate to provide a ground connection when the body is attached to the housing; conducting means insulatingly supported at the other end of the body and adapted to engage electrically the spring; and means for moving the conducting means against the biasing force of the spring to compress the spring out of engagement with the abutment to break the ground connection.

. 2. A condenser and a magneto primary grounding unit adapted to be detachably attached to a magneto housing comprising; a metal body provided with a through opening therein and having an internal abutment intermediate its ends; insulation lining a portion of the opening on one side of the abutment; a metal disc movable within the lining and capable of engaging the abutment; a condenser unit having a metal core supported in one end of the opening with the core spaced from the abutment; a coil spring electrically connected with the core for urging the disc against the abutment, said core, spring, disc when in their normal positions cooperating with the housing to provide a ground connection; and movable means insulatingly supported at the other end of the opening and operable to move the disc from the abutment to break the ground connection. r

3. A condenser and a magneto primary grounding unit adapted to be detachably mounted on a metallic housing comprising in combination; a metal bushing having a bore extending therethrough and being restricted intermediate its ends to provide a, shoulder; a condenser body having a metallic core fixed within one end of the body so that theinner end of the core is spaced from the shoulder; a disc member reciprocatively movable within the bore and between the shoulder and inner end of the core; a helical biasing spring of electrically conducting material between the core and the disc to bias th latter against the shoulder to provide a ground connection for the core; terminal means insulated from the housing normally engaging the disc; and means detachably mounted on the bushing for actuating the terminal which when fastened to the bushing moves the terminal against the bias of the spring to move the disc away from the shoulder to break the ground connection, and which when removed from the bushing permits the spring to move the disc against the shoulder to make the ground connection,

4. A grounding unit for the primary circuit of a magneto comprising the combination, of a metal bushing adapted to be detachably mounted to a metal housing of a high tension ignition device and having a central bore therethrough and being internally restricted intermediate its ends to provide a shoulder; an insulating tube having a sliding fit within the bushing and bearing against the shoulder; a metal disc loosely supported Within the tube; a condenser unit fixed within the metal bushing and adapted to seat against a second shoulder to hold the insulating tube against the first shoulder, said condenser unit having a metal core having one end extending beyond one end of the metal bushing and having the other end extending into the insulating tube; a helical spring of electrical conducting material having one end in conducting relation with the condenser core and having th other end engaging and biasing said metal disc against said first shoulder to provide a ground connection; an internally threaded sleeve threadedly engaged with an externally threaded portion of the body; and conducting means insulated from the sleeve and engaging said disc said sleeve when threaded a certain distance causes the conducting means to move the disc from the first shoulder against the biasing force of the spring to break the ground connection between the metal disc and the metal housing.

5. A unit for support and anchorage of a condenser unit and an insulated conductor in a high tension ignition system comprising in combination; a metal body adapted to be detachably mounted with a metal housing and having a through bore provided with an internal shoulder; an electrical condenser having a metal core positioned within one end of the bore so that one end extends outside the body and the other end is suitably spaced from one side of the shoulder; a spring and a metal disc disposed between the core and shoulder, said spring operating to urge the disc against the shoulder to provide a ground connection through the body; a terminal assembly including an insulating bushing slidably mounted within the bore and positioned on the other side of the shoulder: an insulated wire having one end extending through the bushing, and a conductive member detachably mounted on said end of the cable in conducting relation with the wire thereof, holding the assembled bushing cable and member in fixed position said member extending loosely past the shoulder and into engagement with the disc: and means having threaded engagement with the body for actuating the terminal assembly against the bias of the spring to move the disc away from the shoulder to break the ground connection between the disc and the body.

6. A condenser and magneto primary grounding unit adapted to be detachably attached to a magneto metal housing comprising, a metal body having threaded engagement with the housing, said body having a through opening and being provided with an internal ledge; a condenser having a metal core supported on one side of the ledge with one end of the core spaced from the ledge; a yieldabl conducting means having one end engageable with the core and the other end engageable with the ledge to provide normally a ground connection through the body; an insulating sleeve slidably supported by the body and located on the other side of the ledge; a contact member carried by the sleeve and cooperating with said spring to control the ground connection through the body; and means detachably carried by the body and operable to actuate the sleev for urging same in a direction causing the contact to move the spring out of engagement with the ledge.

7. In combination with a magneto housing having an opening in one wall thereof; a readily attachable and detachable primary grounding unit adapted to fit in the opening, said unit including a hollow metal body, a condenser unit having a metal core fixed in one end of the body, a conducting spring adapted to connect the core with the body to provide a ground connection through body, an insulated conductor disposed movably at the other end of the body and adapted to engage the spring, and detachable means for holding the conductor in assembled relation with the body, said means being adjustable to enable the conductor to be moved to compress the spring so that the latter is moved out of engagement with the body to break the ground connection through the body.

8. A condenser and a magneto primary grounding unit adapted to be detachably attached to a magneto metal housing comprising, a hollow metal body; a condenser unit having a metal core supported in one end of the body; a conducting spring having one end electrically connected with one end of the core and having the other end adapted to engage a part of the body to provide a ground connection through the body; insulation lining a portion of the body and surrounding the spring between the condenser and th part; and detachable means insulatingly supported at the other end of the body and operable to compress the spring end out of engagement with the part and within the confines of the lining to break the ground connection and maintain th spring in its compressed state until the detachable means is substantially removed from the body.

HERMAN L. HARTZELL. 

